audio-filter 
WORK IN PROGRESS, please get back after a while to not get disappointed.
Collection of digital filters, for audio & dsp applications.
Usage

Produce 1024 samples of grey noise:
const WhiteNoise = require('audio-noise/white')
const LoudnessFilter = require('audio-filter/loudness')
let noise = WhiteNoise()
let filter = LoudnessFilter()
let data = filter(noise(new Float32Array(1024)))
API
Filters can be used separately as require('audio-filter/<type>') or as a bundle require('audio-filter').<type>. Every filter constructor creates a filtering function based on options. options may provide filter-specific parameters, usually numbers or functions for varying parameters.
const createFilter = require('audio-filter/<some>')
let filter = createFilter(options)
let data = filter(samples)
Implemented filters:
Filters
leaky({lambda: 0.95, y: 0})
Leaky integrator.
See also
- a-weighting — collection of frequency weighting curves.